Two techniques for repair and strengthening masonry ...Two techniques for repair and strengthening...

Structural Analysis of Historical Constructions - Modena, Lourenço & Roca (eds) © 2005 Taylor & Francis Group, London, ISBN 04 1536 379 9

Two techniques for repair and strengthening masonry constructions

R.A. Sofronie UNESCO Eco/and, Bucharest, Romania

ABSTRACT: The paper refers to masonry based on burned clay bricks and lime mortars currently used to historical constructions. Theory of dislocations is used to explain the mechanism of damaging the masonry in structural members, but also to prevent any failures in the same members. There are two techniques for repair and strengthening masonry in historical constructions: reinforcing structural members with polymer grids and confining them with the same synthetic reinforcement embedded in lime or lime-cement mortars. Two numerical examples of designing shear walls are presented. The results show that polymer grids enhance the shear capacity of the weakest sections of walls, and economically the two techniques are extremely attractive.

INTRODUCTION

Romanian historical constructions like three-Iobed churches, castles, palaces and walls of defence are made of genuine masonry. It is the original artificial stone based on burned clay bricks and lime mortars. This masonry was produced with the aid of gravity and remained dependent for ali its service life on gravity. Solid porous bricks are elastic but brittle, while lime mortars by spontaneous plastic defortnations protect them. When damaged by earthquakes, for instance, or decayed by long time actions of environmental factors this type of masonry can not be recovered but with the same or compatible materiaIs. Cement mortars are not appropriate beca use their thermal coefficient of expansion is 2.5 times higher than that of masonry. If associated, under daily variations of temperature, the two materiaIs are differently dilating or contracting, and afier a while they are detaching one of another. On the other hand ifreinforced concrete members like columns and beams are used for confining masonry on ali four sides they are inducing structural non-homogeneity what is against of EC8 principIes.

2 THEORY OF DISLOCATJON

According to the well known hypothesis of Jacob Bernoulli ifa continuous, homogeneous and isotropic structural member is submitted to a concentrated force then the resulting stresses in equilibrium state are unifortnly distributed. The stresses are proportional with the ratio between the value of force P and the area of cross-section A. This relation is currently used is designo However, if somewhere a structural fault

735

<J= ~= consl.

Homogeneous

Fault (Crack, Void)

Figure I. Stresses under a concentrated force.

occurs or is deliberately provided Bernoulli 's hypothesis does not subsist. Around the fault a concentration of stresses develops. Ifthe material ofstructural member is brittle then according to Lev Landau, Nobel prised for Physics, the stress concentrations could originate dislocations (Fig. I).

Particularly, the structural members of masonry are essentially non-homogeneous. Masonry is far to be a continuous and isotropic material. From the point of view of Theory of dislocation the vertical joints

cr=f=const.

Homogeneous

Fau ll (Crack. Void)

Figure 2. Grid superposed over the fault.

between bricks are like permanent faults. For long lasting actions like the gravitational ones the ductility of lime mortars protects the bricks against fa ilure by the phenomenon known as adaptation. In the case of short time actions like those developed during earthquakes there is no time left for plastic deformations to redistribute the concentrated stresses. An efficient solution to prevent dislocations or fa ilures and thus protect masonry is to superpose over the fault a grid. Due to its regular geometry and high strength to tension the stresses are redistributed among neighbouring sections avoiding masonry damage (Fig. 2).

Since such faults are everywhere in masonry the whole surfaces of structural members should be accordingly covered. Local interventions are less efficient (Coburn & Spence 2002).

3 PRACTICAL TECHNIQUES

There are many types of grids on the market but they are not suitable for such purposes. Steel grids. for instance, have apertures toa large, comparing with masonry are toa strong and for corrosion protection they should be embedded in cement mortar what is incompatible with masonry. The most appropriate reinforcement is based on polymer grids with solid integrated joints. They satisfy ali the geometrical and mechanical requirements for such interventions.

DSF3 825 +'Ic,<

"O

~ Q)

~ o C - ·Cü a:

DSF2 +5",50

lO C\l

cri ~ ..c

DSF1 2",75

"O

~l Q) c 'E o u

tO",OO

1-5.50 25 25

Figure 3. View and vertical cross-sections.

There are two techniques for repair and strengthening masonry in historical constructions. One consists in reinforcing the vertical surfaces of structural members with sheets of polymer grids applied over masonry joints with great care for a good anchoring of render. The other technique consists in confining the structural members by wrapping them around with the same sheets of grids and also with great care for good anchoring. Both techniques are reversible and when necessary can be easily detached and replaced (Sofronie & Feodorov 1995).

4 DESIGN EXAMPLES

An existing masonry wall with the length 1= 5.50 m, height ho = 8.25 m and thickness t = 25 cm has the design compression strength fd = IA MPa and corresponding shear strength fv = 0.2ao, unit weight Ym = 18 kN/m3 and friction coefficient in horizontal joints /.L = 0.3. In f irst alternative lhe wall is re inforced on one side with a sheet of polymer grids RG20 with the design strength R = 20 kN/m and a reduction factor Yr = 0.85, according to the recommendations contained in RG Manual (Sofronie 2004a). In the second alternative the wall is confined by wrapping around with the same type ofreinforcement RG20 (Fig. 3).

Calculate in-plane design shear forces (DSF) according to capacity design principies at the leveis of potential non-structural floors ±O.OO, + 2.75 and +5.50 when the wall is submitted lO a vertical permanent load proportional with its own weight N = 1.788 G and emphasise the contribution of shear reinforcement. The approximate and simplified method adopted fo r this demonslrative example is currently

736

I: Cf 0"2.23 g I

'","".46 • ~ gJ 1=5.50

Figure 4. Cross section at ±O.OO.

used in countries with seismic activity (Paulay & Priestley 1992).

DESIGN VERTICAL LOADS

Levei ±O.OO: No = 1.788 x 18 x 5.50 x 0.25 x 8.25 = 365 kN

Levei +2.75: N, = 1.788 x 18 x 5.50 x 0.25 x 5.50 = 243kN

Levei +5.50: N2 = 1.788 x 18 x 5.50 x 0.25 x 2.75 = 122kN

PLAIN MASONRY (PM)

I. Shear in eccentric compression

Levei ±O.OO: No = 365kN, aspect-ratio 1/ ho = 0.67.

Area of compressed zone in the ultimate limit state (Fig.4):

A = No = 365 = 0.26m 2 " /d 1400

(I)

Length of compressed zone

ç =~= 0.26 =1.04m t 0.25

(2)

Eccentricity of compression force

e = 1/ 2 -ç / 2 = 0.5x(5.50-1.04) = 2.23m (3)

Moment of compression force

I: 1- 1;=4.81

1=5.50

e=2.41

Figure 5. Cross section at +2.75.

cF e=2.58

I: 1-1;=5.15

1=5.50



ç =~ = 0.174 = 0.69m t 0.25

Eccentricity of compression force

~ .- ç •

e = li 2 - ç /2 = 0 .5x(5.50 - 0.69) = 2.4lm


M e = N,e = 243x2.41 = 585 .63kNm

Shear force afferent to moment

v = 3Me = I 5x 585 .63 = 160kN , 2h, . 5.5

I~

(7)

(8)

(9)

(lO)

Levei +5.50: N2 = 122 kN, aspect-ratio l/h2 = 2.00

Area of compressed zone in the ultimate limit state (Fig.6):

A = N 2 = 122 = 0.087m 2

" /d 1400 (11)


M, = Noe = 365x2.23 = 813 .95kNm (4) ç = ~ = 0.087 = 0.35m t 0.25

(12)

Shear force afferent to moment Eccentricity of compression force

v = 3M, = I 5x 813.95 = 148kN , 2ho . 8.25 (5) e = 1/ 2 - ç /2 = 0.5x(5.50 - 0.35) = 2.58m

Levei +2 .75 : N, =243kN, aspect-ratio l / h I = 1.00.

Area of compressed zone in the ultimate limit state (Fig. 5):

A = N , = 243 = 0.174m 2

" /d 1400 (6)

737


Me = N 2e = 122x2.58 = 314.76kNm

Shear force afferent to momen!

(13)

(14)

(15)

2. Shear in inclined sections

Levei ±O.OO: No = 365 kN

Compression stress in masonry cross-section

N 365 u = _o = = 265 45kPa

o Am 5.50x0.25 .

Shear strength

1., = 0.20' o = 0.2x265.45 = 53kPa

Shear force in plain masonry

v, = J.,A", = 53x5.5xO.25 = 73kN

Levei +2.75: N1 = 243 kN


N I 243 O' = - = = 176 73kPa

o A", 5.50xO.25 .

Shear strength

I, = 0.20' o = 0.2x I76.73 = 35.35kPa


V; = I ,A", = 35.35x5.5xO.25 = 49kN

Levei +5.50: N2 = 122 kN


O' = N 2 = 122 = 88 73kPa o A", 5.50xO.25 .

Shear strength

1., =0.20'0 =0.2x88.73= 17.75kPa


V; = I ,A", = 17.75x5 .5xO.25 = 24kN

3. Shear in horizontaljoints



VJ

=)lHo = 0.3x365 = II0kN

Levei +2.75: N1 = 243 kN

(16)

(17)

(18)

(19)

(20)

(21)

(22)

(23)

(24)

(25)

Table I. Design shear forces in the wall af plain masonry.

Eccentric lnclined Horizontal compression sections joints

Levei Ve (kN) Vi (kN) Vj (kN)

± O.OO 148 73 110 +2.75 160 49 73 +5 .50 172 24 37


Vj = tiNI = 0.3x243 = 73kN (26)

Levei +5.50: N2 = 122kN


Vj =)lH2 = 0.3x122 = 37kN (27)

The results of shear analysis are comparatively presented in Table 1.

Comments:

I) Shear capacity in eccentric compression is strongly influenced by wall aspect-ratio. Sub-w1itary aspectratios mean column-effect while supra-unitary ones wall-effect.

2) Shear capacity in inclined sections and horizontal joints is not influenced by aspect-ratio modification.

3) The weakest shear capacity ofwall is in inclined sections. That means when submitted to seismic actions the wall is in danger to crack in form ofX-shape at ali leveis. The shear capacity of the upper levei is only one third of that of ground leveI.

REINFORCED MASONRY (RM)

1. Shear in eccentric compression

LeveI ±O.OO: No = 365 kN, aspect-ratio Il ho = 0.67. Forces on cross-section (Fig. 7):

Cm = (0.25';)xI400 = 350';

C, = 20';

T, = (5.5 -';)x20 = -20'; + 11 0

Equilibrium equation

350.; + 20'; - (-20'; + 110) = 365;

(28)

(29)

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RG20 em=2.14

~ .. ~ .. ~ .. ~. ~~.~.~ .. ~ .. ~ .. ~. ·~·lt· .~.~ .. ~ .. ~ .. ~ .. ~.~ .. ~.L~ .. ~ .. ~ Kl

I s I·S=4.28

1=5.50

T, CG

er=0.61

Figure 7. Cross section at ±O.OO.

Neutral axis

.; = 365+110 = 475 =1.22m 350+20+20 390

Values of forces

(30)

RG20 em=2.30 .~ ..•. ......... I. ................. I ••• • ~ __________ ~+~ ______ ~~/~~~-+ Kl

1 s I·S=4.60

1-5.50


Neutral axis

.;= 243+110 =353=0.90m 350+20+20 390

Values offorces

Cm = 350xO.90 = 315kN

(37)

Cm = 350xl .22 = 427 kN

C, = 20xl.22 = 24.4kN

T, = -24.4 + 110 = 85 .6kN

(31) C, = 20xO.90 = 18kN

T, = -18 + Ii O = 92kN

(38)

Eccentricities of forces

em = 0.5x(5.50 -1.22) = 2.14m

e, =em =2.14m (32)

e, '= 0.5x1.22 = 0.61m

Moment in the ultimate limit state of eccentric com· pression


em = 0.5x(5.50 - 0.90) = 2.30m

e, = em = 2.30m

e, '= 0.5xO.90 = 0.45m

(39)

Moment in the ultimate limit state of eccentric compresslOn

M e = (427 + 24.4)x2. 14 +85.6xO.61 = 1018.21kNm (33) M e = (315 + 18)x2.30 + 92x0.45 = 807.3kNm (40)


v, = 3M, = l.5x 1018.21 = I 85kN 2ho 8.25

(34)

Levei +2.75: N 1 =243kN, aspect-ratio I/ h l = 1.00.

Forces on cross-section (Fig. 8):


v = 3M e = l.5x 807.3 = 220kN ' 2~ 5.50

(41)

Levei +5.50: N2 = 122kN, aspect-ratio l / h2 =2.00


C", = (0.251; )x1400 = 350'; C", = (0 .25';)xI400 = 350';

C, = 20'; (35) C, = 201; (42)

T, = (5.5-';)x20 = - 20'; + 110 T, = (5.5 - ';)x20 = -20'; + 110

Equilibrium equation Equilibrium equation

I X = o; c'" + c, - T, = N 2 ;

350.; + 20'; - (-20'; + Ii O) = 243; (36) 350'; +20'; -(-20'; + 110) = 122; (43)

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RG20 em=2,45 .~ .. . .. .. .. .... I. .... ... .. .. .... .. .l .. ~ ____________ 4~ _________ ~~~-+~

1-1;=4.90 I I; 1=5.50


Neutra l axis

ç = 122 + I 10 = 232 = 0.60m 350 + 20 + 20 390

(44)

Values of forces

Cm = 350xO.60 = 21 OkN

C, = 20xO.60 = 12kN

T, = - 12 + Ii 0 = 98kN


em = 0.5x(5.50 - 0.60) = 2,45m

e,. = em = 2.45m

e,' = 0.5xO.60 = 0.30m

Figure 10.

Table 2.

(45)

Levei

±O.OO +2.75

(46) +5.50

View of incJined cracks at pure shear.

DSFs in the wall of reinforced masonry.

Eccentric IncJined Horizontal compression sections joints Ve (kN) Vi (kN) Vj (kN)

185 159 196 220 135 159 313 67 123

Moment in the ultimate Iimit state of eccentric com- 3. Shear in horizonta!joints

presslOn Levei ±O.OO: No = 365 kN

M e = (2 10 + 12)x2.45 + 98xO.30 = 573.3kNm


2. Shear in inclined sections (Fig. la)


Shear force from reinforcement

V; = r , R! = 0.85x20x5.50 = 86kN

Levei +2.75: N1 = 243 kN


V, = r , R! = 0.85x20x5.50 = 86kN

Levei +5.50: N2 = 122 kN


r'; = r,Rh2 = 0.85x20x2.75 = 43kN

(47) Shear force from reinforcement

Vj = r,R! = 0.85x20x5.50 = 86kN (52)

(48) Levei +2.75: N1 = 243 kN


VJ

= r,R! = 0. 85x20x5.50 = 86kN (53)

Levei +5.50: N2 = 122 kN

(49) Shear force from reinforcement

Vj = r ,R! = 0.85x20x5.50 = 86kN (54)

The results of shear analysis are comparatively pre-(50) sented in Table 2.

(51)

Comments:

1) Reinforcement enhances the shear capacity in ali the three limit states offailure, but mostly the weakest state of wall, namely that of principal stresses in inclined sections .

740

Table 3. Ratio RMlPM x 100 due to one sheet RG20.

Eccentric Inclined Horizontal compression sections joints

Levei (%) (%) (%)

±O.OO 125 218 178 +2.75 138 276 218 +5.50 182 279 332

2) Mortar in which reinforcement is embedded does not appear explicitly in any analysis. rts role of matrix is only to provide the mechanism of stress transfer from masonry to polymer grids. For this reason lime mortar is recommended because the strength comes from reinforcement. The thickness of render can be as thin as to cover the reinforcement, for instance 20 mm.

3) The wall is uniformly reinforced from bottom to top with the same polymer grids RG20 providing continuity and homogeneity as requested by EC8 principies (Sofronie 2002).

The ratios between shear forces for reinforced masonry and plain masonry are comparatively presented in Table 3.

Comments:

I) The efTect of reinforcement is high exactly in the needed sections where pure shear could occur. The cost of reinforced masonry compared with plain masonry is 119%.

2) Higher mechanical performances can be obtained either by using stronger grids like RG30 or by reinforcing both sides ofwall with the same grids RG20. However, the proportion between shear capacity of masonry and that of reinforcement is recommended to remain between 1/3 and 3/1.

3) The above described method of seismic protection can be similarly applied to flanged cross-sections like L, I, T, U profiles with care for fixing the grids along the inner corners.

CONFrNED MASONRY (CM)

As a consequence of confining by wrapping the wall around the compression strength ofmasonry increases with 25% to fd = 1.25 x IA = 1.75 MPa, while the shear strength and friction coefTicient in horizontal joints became fv = 0.25ao and !-lo = 004 , respectively. The reduction factor Y .. is also increasing but for sake of simplicity in analysis was used the same value.

I. Shear in eccentric compression

Levei ±O.OO: No = 365 kN, aspect-ratio I/ ho = 0.67.

741

em=2.19

I

l-ç=4.37

1-5.50

Figure 11. Cross section at ±o.oo.

Forces on cross-section (Fig. 11 ):

em = (0.25Ç")xI750 = 437.5Ç"

er = 2x20Ç" = 40Ç"

Tr = (5.5 - Ç")x2x20 = -40Ç" + 220


1

437.5Ç" +40Ç" - (-40Ç" +220) = 365;

Neutral axis

ç = 365 + 220 437.5 + 40 + 40

Values of forces

~=U3m 517.5

em = 437.5x1.l3 = 494kN

er = 40xl.13 = 45kN

Tr = -45 + 220 = I 75kN


em = 0.5x(5.50 -1.13) = 2.19m

e r =e",=2.19m

e, '= 0.5xl .13 = 0.57m

I l1') C\I

ç

(55)

(56)

(57)

(58)

(59)

Moment in the ultimate limit state of eccentric compression

M, = (494 + 45)x2.19+ 175xO.57 = 1280. 16kNm

(60)

Shear force afTerent to moment

v = 3M, = 1 5x1280.16 = 233kN e 2ho . 8.25

(61)

e 230

-~ m=

J .I. ~~

1-1;=4.60 'r I;

1=5.50

Figure 12. Cross seclion aI +2.75.

l!J C\J

RG20 m= ~ .I.

e 242

1-1;=4.84

1=5.50

Figure 13. Cross seclion aI +5.50.

.I. WdW

I I;

l!J C\J

Levei +2.75: N l = 243 kN, aspect-ratio l/ h l = 1.00.


Levei +5.50: N2 = 122 kN, aspect-ratio 1/ h2 = 2.00


em = (0.25ç)xI750 = 437.5ç

er = 2x20ç = 40ç

Tr = (5.5 - ç)x2x20 = -40ç + 220


" X = o· e + e - T = N . "t.... 'm r r l'

437.5; + 40ç - (-40; + 220) = 243;

Neutral axis

ç = 243 + 220 = 463 = 0.90m 437.5+ 40+ 40 517.5

Values of forces

em = 437.5xO.90 = 394kN

er = 40xO.90 = 36kN

Tr = -36+ 220 = 184kN


em = 0.5x(5.50 - 0.90) = 2.30m

er = em = 2.30m

er '= 0.5xO.90 = 0.45m

em = (0.25Ç)xI750 = 437.5Ç

(62) er = 2x20ç = 40ç

(63)

(64)

Tr = (5.5 - ;)x2x20 = -40ç + 220


"x=oe +e -T =N' ~ 'm r r 2'

437.5ç +40ç -(-40ç +220) = 122;

Neutral axis

ç = 122 + 220 = 342 = 0.66m 437.5+40+40 517.5

Values of forces

em = 437.5xO.66 = 289kN

er = 40xO.66 = 26.4kN

(65) Tr

= -26.4 + 220 = 193.6kN


em = 0.5x(5.50 - 0.66) = 2.42m

er = em = 2.42m

(66) er '= 0.5xO.90 = 0.33m

(69)

(70)

(71 )

(72)

(73)

Moment in the ultimate limit state of eccentric Moment in the ultimate limit state of eccentric compression compression

Me = (289+ 26.4)x2.42 + 1936xO.33 = 827. 16kNm

M. = (394+36)x2.30+184x0.45=1071.8kNm (67) (74)

Shear force afferent to moment Shear force afferent to moment

v = 3M. = 1 5x 1071.8 = 292kN • 2ho . 5.50

(68) v = 3M. = 1 5x827 16 = 451kN • 2ho . 2.75

(75)

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2. Shear in inclined sections


Shear force in confined masonry

V; = O.25No + 2yrRl =

O.25x365 + 2xO.85x20x5.50 = 278kN

Levei +2.75: N 1 =243kN


V; = 0.25N\ + 2YrR1 =

O.25x243 + 2xO.85x20x5.50 = 248kN

Levei +5.50: N2 = 122 kN


v, = O.25N2 + 2YrR1 =

O.25x122 + 2xO.85x20x2.75 = 124kN

3. Shear in horizontaljoints



v} = J.1No + 2YrR1 =

0.4x365 + 2xO.85x20x5 .50 = 333kN

Levei +2.75: N 1 =243kN


V j = J.1N\ + 2YrRl =

0.4x243 + 2xO.85x20x5 .50 = 284kN

Levei +5.50: N2 = 122kN


Vj = J.1N2 + 2Yr R1 =

0.4x122 + 2xO.85x20x5 .50 = 236kN

(76)

(77)

(78)

(79)

(80)

(81)

The results of shear analysis are comparatively presented in Table 4.

Comments:

I) Shear capacity ofwall is continuing to be influenced by aspect-ratio. The weakest shear capacity of wall is to eccentric compression at the levei ±O.OO and to principal stresses in inclined sections at the leveis +2.75 and +5.50.

2) The highest influence of confining is in inclined sections at leveis ±O.OO and +2.75 and in horizontaljoints at the levei +5.50. However, the proportion between shear capacity ofmasonry and that ofreinforcement is recommended to remain between 1/5 and 5/1 .

Table 4. DSFs in the wall of confined masonry.

Eccentric IncIined Horizontal compression sections joints

Levei V e (kN) V i (kN) Vj (kN)

±o.oo 233 278 333 +2.75 292 248 284 +5.50 451 124 236

Table 5. Ratios CMlRM x 100 and CMlPM x 100.

Eccentric IncIined Horizontal Levei compression sections joints

±O.OO 126% 157% 175% 381 % 170% 303% +2.75 133% 183% 184% 506% 179% 389% +5.50 144% 262% 185% 517% 192% 638%

3) Confined masonry is a true composite material. The cost of confined masonry compared with that of plain masonry is 138%.

The ratios between design shear forces for confined and reinforced masonry as well as confined and plain masonry are comparatively presented Table 5.

Comments:

I) The effect of confinement is large exactly in the sections it is necessary, namely there where pure shear can occur.

2) Comparing with reinforced masonry the confinement enhances the shear capacity almost from simple to double.

3) Comparing with plain masonry the confinement enhances the shear capacity from almost four to six times.

4) In confined walls the openings for doors and windows should be avoided. If that is not possible the corners ofthe openings should be additionally reinforced according to Manual provisions (Sofronie 2004b,c) .

5) The sheets of reinforcement are joined by superposition over a length of minimurn 400 mm.

5 CONCLUSIONS

I. Polymer grids used for reinforcing or confining masonry enhances the shear capacity of walls in buildings and structures. The merit of grids is first due to the fact they are acting on the whole surface of walls not locally only. Secondly by their regular geometry the grids contribute to standardize the stresses and prevent stress concentrations around faults, which originate dislocations. Finally,

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due to high strengths of grids the reduced tensi le resistances of mortars are substituted and lime or lime-cements can be used for plastering.

2. The remarkable quality of RichterGard System is reversibility. Indeed, in case of damage or changing the construction approach the synthetic reinforcement can be easily detached and replaced with a new one in accordance wi th the new requirements.

3. The relation geometry-matter is not limited to pure shear only. In the sections with high aspectratios where the compression force is diminishing the friction is reduced and consequently the shear capacity in horizontal joints decreases. The thickness of plaster loses its significance comparing with the strength of grids. The relative cost of reinforcing or confining also depends by the ratio between the surface on which the grids are applied and the volume of masonry. It is more convenient to reinforce massive masonry members than slender walls or columns. However, the most important effect of RichterGard System remains the uniform distribution of stresses on wall surfaces with the aid of polymer grids used as reinforcement.

4. The comparative economic analysis presented in the paper was limited only to the cost of materiais, namely of masonry and reinforcement. A comprehensive analysis should include the low cost and high productivity of labour as well as the short duration of construction.

5. There are also other severa I applications of the two techniques for repair and strengthening masonry in historical constructions. One is to support thermal isolation Iike foam glass plates or others. Then seismic protection of brick veneers and curtain walls. Finally, due to their capacity of avoiding stress concentrations, the walls reinforced or confined with polymer grids are well protected against terror

attacks. There is not at ali much trouble to apply the method to the existing constructions.

ACKNOWLEDGMENTS

The financiai support of the European Commission DGXIl for Science, Research & Development through the INCO Copernicus Project ICI5-CT96-0203 Euroquake and Ecoleader-Seriate Program is gratefully acknowledged. Thanks are also due to RichterGard Company, based in Blackburn UK, fo r supplying the polymer grids used in testing programs.

REFERENCES

Coburn, A. & Spence, R. 2002. Earthquake Protection. Second Edition. London: John Wiley & Sons.

Paulay, T. & Priestley, M.J.N. 1992. Seismic design of rein-forced concrete and masonry buildings. New York: John Wiley & Sons.

Sofronie, R. & Feodorov, V 1995 . Method of seismic reinforcement ofmasonry works. Bucharest: Romanian Patent Office RO 112373 B I.

Sofronie, R. 2002. Repair and retrofitting masonry buildings. Proceedings of the 12th European Conference on Earthqllake Engineering. Barbican Centre, London UK, Paper Reference #183.

Sofronie, R. 2004a. Design and Installation Manual for seismic protection of existing buildi ngs with RichterGard System in accordance with ISO 13822:2001(E).

Sofronie, R. 2004b. Seismic strengthening of masonry in buildings and cultural heritage. Proceedings of lhe 6th National Congress on Earthqllake Engineering. Sismica 2004. University ofMinho, Guimarães, Portugal. pp. 81- 100.

Sofronie, R. , 2004c. Performances in seismic strengthening of masonry. Proceedings of the 13th World Conference on Earthquake Engineering. Vancouver, B.C., Canada. Paper No. 182.

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